typedef union __AXPBRMTIIR { AXPBLPF lpf; AXPBBIQUAD biquad; } AXPBRMTIIR;
By setting rmtIIR appropriately, you can apply an IIR filter to the audio output from the Controller speaker.
The IIR filter is applied on the AX voice process pipeline just before the audio data is converted from 32 kHz for the main speaker to 6 kHz for the Controller speaker.
As the IIR filter for the Controller speaker, choose either LPF or Biquad filters. Both types of filters are used in basically the same way as the filters for the main speaker (i.e., axvpb.pb.lpf and axvpb.pb.biquad).
The difference is that the two types of filters cannot be used at the same time.
The method to reflect the filter parameters in the DSP is also different. When LPF filters have been selected, in order for changes to the filter coefficients a0 and b0 to be reflected in the DSP, you must assert the AX_SYNC_USER_RMTIIR_COEF1 bit in the axvpb.sync member. When Biquad filters have been selected, in order for changes to the filter coefficients b0 to a2 to be reflected in the DSP, you must assert the AX_SYNC_USER_RMTIIR_COEF2 bit. When the filter switch on is changed, you must assert the AX_SYNC_USER_RMTIIR bit so that the entire AXPBIIR union is reflected in the DSP.
The IIR filter for the Controller speaker is independent for each voice, so you can select whether to turn the filter on/off, which filter type to use, and the cut-off frequency for each voice audio data. Note also that because the IIR filter for the Controller speaker operates independently of the LPF and Biquad filters for the main speaker, you can use different cut-off frequencies for the main speaker and the Controller speaker at the same time.
Note: In order to correctly specify the filter type (LPF or Biquad) for the IIR filter for the Controller speaker, you must set the appropriate value to the on member of the structure for each type. To use LPF filters, specify AX_PB_LPF_ON(1). To use Biquad filters, specify AX_PB_BIQUAD_ON(2). If you are using neither type of filter, specify AX_PB_LPF_OFF/AX_PB_BIQUAD_OFF(both 0).
axvpb.pb.lpf
axvpb.pb.biquad
axvpb.sync
AXSetVoiceRmtIIR
AXSetVoiceRmtIIRCoefs
2006/11/14 Initial version.
CONFIDENTIAL